Measurement of respiration effort is required to diagnose or monitor various diseases ranging from emphysema to sleep apnoea. Generally the devices used for measurement use some sort of mask which is cumbersome and is often inconvenient and uncomfortable for a subject to wear.
Also, variation of chest circumference at the diaphragm is a clear indication of respiration effort. It has been shown by electromyography (EMG) measurement that to diaphragm activity is linked with sleep apnoea.
In some cases it is useful to monitor cardiac function in addition to respiratory function.